A number of patents have issued to one Constant Johan Nauta of Overveen, Netherlands covering both single screw mixers and multiple screw mixers. A search of the United States patent art has not been made with reference to the specific invention herein claimed but it is believed that perhaps U.S. Pat. No. 3,109,633 Nauta is representative of a single screw mixer while U.S. Pat. No. 3,450,390 Nauta may be representative of a multiple screw mixer of the general type to which the present invention may be applied.
In prior arrangements each of the twin screws has been supported from cantilevered arms, the lower bearings carrying no weight and serving only as guides. In such prior arrangements, however, a ball bearing system was incorporated in the lowermost end of each screw and this system was received on an upstanding shaft positioned on a lower support which rotated at the same speed as the cantilevered arms. The ball bearing guide system was drivingly engaged by the screw through metal to metal contact which required a specially treated, hardened surface and also a specially machined surface to permit accommodation of linear deflection as caused by the forces, including heat, encountered during mixing.
The purpose of the instant invention is to improve the lower guide bearing arrangement for the screws of a twin screw mixer so as to eliminate the necessity for special machining and the use of special hard surfaces.